Setext header marker equalization on ENTER broken

[vsch]

The added equalization inserted after EOL.

[vsch]

Actually, the equalization is done right but the caret was not adjusted to the end of marker before passing control back to original handler which inserted an EOL.

[vsch]

Another issue is for equalization when the header markers are on the last line of the file without a trailing EOL.

In this case no equalization was done.

Related but wrap on typing would wrap after the third - or = was typed, not recognizing it as a setext marker line.